This invention relates to a thermoplastic resin composition which is excellent in impact resistance, heat resistance, and appearance and color hue of a molded product.
A polyphenylene ether (hereinafter referred to as "PPE") has been known as engineering plastics having excellent mechanical characteristics and heat resistance, and has been used by mixing with a styrene resin or others. However, it has drawback that solvent resistance is markedly bad and, in order to overcome the drawback, there have been proposed a blended material with a polyamide (e.g. Japanese Patent Publication No. 41663/1984) or a blended material with a polyester resin (e.g. Japanese Patent Publication No. 21662/1976).
However, in such a simple blend system, PPE and the polyamide resin have inherently poor compatibility with each other so that adhesiveness at an interface of this two phase structure is not good, whereby two phases can hardly take uniform and fine forms. Therefore, when shear stress is applied to molding processing such as injection molding, laminar peeling (delamination) is easily caused, whereby appearance of a resulting molded product is worsened and an interface of two phases becomes a defective portion. Thus, it is impossible to obtain a composition having excellent mechanical characteristics such as dimensional stability, heat resistance and rigidity and excellent physical characteristics such as solvent resistance.
Therefore, in order to improve compatibility with the blended resin and to improve impact resistance, a composition in which a compound having a polar group such as a carboxyl group, an imide group and an epoxy group and a rubbery material as an impact modifier are added to the composition comprising PPE and a polyamide resin has been proposed (Japanese Provisional Patent Publication No. 9753/1984).
In the above technique, whereas compatibility has been improved with a certain degree by using the impact modifier, new problem arises that a heat distortion temperature is lowered.
Also, such a polyphenylene ether resin composition has been utilized for an out-side plate material of an automobile such as a fender and door panel. However, since a large scale product is molded at a high temperature, an insufficient product is frequently produced, which is caused by a poor thermal stability, such as yellowing and silver streaking on the surface of the molded product.
Further, when a conventional compatibilizer such as maleic anhydride as described in Japanese Provisional Patent Publication No. 28248/1990, the problem occurred that color hue of the blended material becomes bad.